The invention is related to a method and apparatus for the concentration and separation of actinide values from samples containing these and other elements. More specifically, the invention relates to a method and apparatus for the quantitative recovery of antinide values from biological and environmental samples. Still more specifically, the invention relates to a method for the quantitative recovery and detection of actinide values from biological samples such as urine, blood and feces and from enviromental samples such as soil and water and to an apparatus for accomplishing the same.
The wide-scale use of nuclear technology, both in power production and in the manufacture of nuclear weapons, necessitates the periodic monitoring of biological and environmental samples for the presence of selected antinide elements; e.g. Th, U, Np, Pu, Am and Cm. The most common types of samples assayed are urine and fecal material. Recent world events such as the power reactor explosion at Chernobyl in the USSR, point up the need for quick, effective and accurate methods for monitoring environmental samples of soil and water to determine the degree of distribution and concentration of the actinide elements, as a group and individually.
A number of procedures for the determination of the actinide plutonium in urine are disclosed in Mikrochimica Acta 1978 1, pages 79 to 88. As discussed therein, procedures for the preconcentration of extremely small amounts of Pu (about 10.sup.-11 -10.sup.-12 g) from the vast excess of matrix substances present in urine samples include: precipitation reactions, absorption on glass fibre, extraction, extraction chromatogrophy and ion exchange. Of these, the precipitation reactions provides the most economical results.
As described in the article, the present method for recovering Pu from urine samples requires the addition of nitric acid and a small amount of calcium ions and phosphoric acid to the sample which is then heated for about 3 hours to digest the proteinaceous material normally found in urine, releasing the Pu. Concentrated ammonia solution is then added to co-precipitate calcium phosphate and the Pu. The precipitate is then dissolved in HNO.sub.3 and evaporated to dryness several times to wet-ash any remaining organic matter. Solid sodium nitrite and nitric acid are added to this residue and the mixture is heated to prepare a nitric acid sample solution suitable for anion exchange. After passing the sample solution through the anion exchange column to recover the Pu, the column is washed several times before the Pu eluted with a dilute HCl/HF solution. Following evaporation to dryness, the residue is dissolved in an appropriate solution and the Pu is electrodeposited. The alpha count is then obtained to determine the quantity of Pu present.
From the above, it is obvious that the Pu recovery process is complex, time consuming and expensive. While the process will also recover Np and Th, it will not recover other actinides, if present. Furthermore, recovery of the various actinides individually is difficult should the detection of each actinide be desired.
Also needed is a method for the quantitative analysis of actinide values which may be found in water and soil samples which is quick, accurate and relatively inexpensive.
U.S. Pat. No. 4,548,790 dated Oct. 22, 1985 describes a group of neutral bifunctional organophosphorous compounds broadly described as alkyl(phenyl)-N,N-dialkylcarbamoylmethylphosphine oxides (hereinafter referred to as CMPO) which are useful for the recovery of actinide and lanthanide values from acidic solutions containing these and other metal values. The combination of the CMPO extractants with a phase modifier such as tri-n-butyl phosphate (hereinafter referred to as TBP) in a normal paraffin hydrocarbon diluent (NPH) diluent is described in U.S. Pat. No. 4,574,072, dated Mar. 4, 1986. Both patents are assigned to the common assignee and are incorporated herein by reference.